Silicone propellant compositions containing nitroguanidine



United States Patent 3,197,349 SilLli-CQNE PROPELLANT COMPOSITIONSCUNTATNTN F lTTRGGUANTDTNE Kiaus Kuhn, Essen-Tiredeney, and TheodorNetzer, Pool:- ing, Eitarnberg, Germany, assignors to NitrochemieG.rn.h.H., Aschau, near Kraiburg, German No Drawing. Fiied Feb. 15,1963, Ser. No. 259,777 12 Ciairns. (Cl. l49-19) The present inventionrelates to propellant compositions, more particularly to propellantcompositions of the solid fuel type, and still more particularly topropellant compositions which are also useful in extinguishers andextinguishing devices.

It is a primary object of the present invention to provide propellantcompositions of the solid fuel type in which the oxidation agent presentacts as a stable source of oxygen supply.

it is another object of the present invention to provide solidpropellant compositions of superior stability which can consequently beused for purposes for which known solid propellant compositions couldnot be used.

Other objects and advantages of the present invention will be apparentfrom a further reading of the specification and of the appended claims.

With the above and other objects in View, the present invention mainlycomprises a propellant composition comprising a propellant which uponoxidation forms gas for propelling purposes (all normal propellants ofthis type being suitable for the purposes of the present invention), andan alkaline perchlorate as oxidation salt which serves as a source ofoxygen for the propellant.

The oxidation salt of the present invention may be any alkalineperchlorate such as sodium perchlorate, potassium perchlorate, lithiumperchlorate, etc., but most preferably is ammonium perchlorate.

In accordance with the present invention the propellant and theperchlorate are distributed through a resin body which is stable at atemperature of 150 C. or more. In accordance with the preferredembodiment of the present invention this resin body is made of asilicone resin.

The perchlorate should most desirably be present in the composition ofthe present invention in a major amount and the propellant in a minoramount. Preferably the alkaline perchlorate is present in an amount ofmore than 50% by weight, most preferably about 60-70% by weight of thecomposition including the resin binding agent and the propellant.

The propellant compositions of the present invention remain stable atelevated temperatures, such as in the environment of a fire, and also atthe high temperatures caused by high speeds, for example, in airplanesand rockets.

This is achieved according to the present invention by the use of analkaline perchlorate as oxidation salt in the propellant composition andalso by the use of a silicone resin as the hinder, the propellant andthe alkaline perchlorate being thoroughly mixed into the silicone resinand the same molded into any desired form.

In extinguishing methods in which in addition to the tire extinguishingagent there is directed onto the site of the fire the greatest possibleamount of gases of combustion, it is advantageous to use ammoniumperchlorate as the alkaline perchlorate. The volume of the gases ofcombustion can be further increased by using in addition to the alkalineperchlorate also nitroguanidine, preferably in an amount of 10-15% byweight of nitroguanidine, calculated with respect to the amount ofperchlorate. The most preferred binding agent according to the presentinvention is a silicone resin having a viscosity of about 30025G0centistokes.

Particularly in the case of airplanes and the like extinguishing devicesare known in which the actual extingushing agent by pressure from gasesof combustion is mixed therewith and is thereby warmed and isnecessarily evaporated and in this manner reaches the site of the fire.Consequently, used liquid propellants, for example, gasoline and oxygen,have the disadvantage that they are separately contained in storagecontainers and for the purpose of producing the actual burning mixtureare exactly dosed by means of conduits and valves and must be mixedbefore they can be ignited. Solid propellants are with respect tostorage and handling less economical. The contained constitutents, as isknown, which are unstable at the occurring high temperatures, and tosome extent at least are decomposed, so that a uniform consumptioncannot be obtained with assurance. This is particularly so with respectto the normally used binding agents.

It is not possible for the purposes of the present invention to use asoxygen carrier any suitable salt because of the question of temperaturestability. For example ammonium nitrate is not suitable because at thetemperatures which occur its crystalline structure undergoes change, andan ammonium nitrate-containing propellant composition for this reasonexhibits changes in solidity upon increased temperature, which isundesired and disadvantageous.

The mixtures of ammonium perchlorate, and propellant, for examplenitroguanidine, with silicone resin, can be molded into solid propellantcompositions according to: the present invention, which even at hightemperatures are of stable form and always burn oif evenly. Moreover,the detona ting temperature of these mixtures is about 260 C., which isvery high, and consequently the stability of the propellant compositionat a temperature of 150 C. is extremely good for a prolonged period oftime.

The following examples are given to further illustrate the presentinvention. The scope of the invention is not, however, meant to belimited to the specific details of the examples.

Example 1 A mixture is made of the following composition:

62. )O% by weight ammonium perchlorate, grain size 6.00% by weightnitroguanidine 29.00% by weight silicone oil (750 centistokes) (methylpolysiloxane) 1.00% by weight aluminum R130 (finely divided aluminumpowder) 2.00% by weight phenanthrene (C I-I There is added thereto 2.5%by weight (calculated with respect to the amount of silicone oil) ofhardener T (alkyl silicate) and 0.5% by weight (calculated with respectto the amount of silicone oil) of hardener T (alkyl silicate) The moldedbody is formed as follows:

The above given amounts of ammonium perchlorate, nitroguanidine andaluminum are thoroughly mixed for 20 minutes at room temperature in akneading device. The mixture is then sifted through a 300a sieve.

The above amount of silicone oil is introduced into a kneading deviceheated to 86 C. The sifted mixture in 4 equal portions is thenintroduced into the kneading device (under stirring), the first tlneeportions being introduced at 15 minute intervals. The fourth and lastportion is then added thereto, the mixture is subjected to a vacuum ofabout mm. Hg and kneading is continued for 120 minutes. The hardener isthen added and the kneading is continued for an additional five minutes.The by now very viscous C. warm fiowable mass is introduced into anair-tight closable draining sas /gees pot over a sieve by means of anunderpressure of about 70 mm. Hg. Then the mass is subjected to anitrogen overpressure in the pot and thereby pressed into cardboardcartridges provided with a form.

The filled cartridges are then (according to the hardener addition)stored at 45 C. for 3 to 8 days, whereby the filled masses are hardenedto removable bodies. After removing the cartridges and the projectionsthe body is cut and wound into the form of a hollow cylinder, which ifnecessary can be provided on the front and the generated surface with aninsulation of a normal silicone oil casting mass filled with oxide.

plus

2.5% by weight (calculated with respect to the silicone oil of hardenerT (alkyl silicate) and 0.5% by Weight (calculated with respect to thesilicone oil) of hardener T (alkyl silicate) The formation of thepropellant composition proceeds as in Example 1.

Example 3 Composition:

31.5% by weight ammonium perchlorate, 60 200 grain size 31.5% by weightammonium perchlorate (wind sifter,

12,000 r.p.m./lg5) 7.0% by weight nitroguanidine 29.0% by weightsilicone oil (750 centistokes) (methyl polysiloxane) 1.0% by weightaluminum R130 (finely divided aluminum powder) plus 3.0% by weight(calculated with respect to the amount of silicone oil) of hardener T(alkyl silicate) The molded body is formed as follows:

The above given amounts of ammonium perchlorate, nitroguanidine andaluminum are thoroughly mixed at room temperature for minutes in akneading device. The mixture is then sifted through a sieve of 300;].and again introduced into the kneading device. The kneading device isthen evacuated to 70 mm. Hg for 10 minutes, kneading is continued for 3minutes and the silicone oil amount is suctioned into the kneadingdevice. The silicone oil addition is heated during 5 minutes to a 8690C. and is kneaded for 45 hours. The hardener is then added and thekneading is continued for an additional 5 minutes.

The very viscous 85 C. Warm fiowable mass is introduced into anair-tight dispensing pot over a sieve by means of underpressure (70 mm.Hg). The mass is then pressed into cardboard cartridges provided withprojections using a nitrogen overpressure of 3 atmospheres in the pot.

The filled cartridges are then (according to the hardener addition)stored for 3 to 8 days at (3., whereby the filled mass is hardened towindable bodies. After removing the cartridges and the projections thebodies are cut and wound into the desired form.

Without any further analysis, the foregoing will so fully reveal thegist of the present invention that others can be applying currentknowledge readily adapt it for various applications without omittingfeatures that,

from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims. The invention as described before may further bevaried in different ways. instead of ammonium perchlorate mentioned inthe examples it is also possible to use as oxidizer the lithium, sodiumor potassium salt of perchloric acid. The silicon resin may be any alkylpolysiloxane such as methy-lpolysiloxane, ethylpolysiloxane or others ormixtures with each other. The viscosity of the silicon resin should liewithin a range of about 3002500 centistokes, but it is also possible tosurpass these limits. The amount of silicon resin added to the mixtureshould be between 10 and preferably 20 to 30% of the total composition.Further ingredients that are added are aluminum powder preferably in afinely divided state and burning stabilisers such as phenanthrene(ortho-di-phenylene ethylene C H an-thracene (C HACHQC HU or othercompounds known per se for this purpose. For hardening the silicon resincontaining mixtures are especially used hardeners on basis of alkylsilicates such as methyl silicates, ethylsilicates or mixtures; but itis also possible to add other known hardeners. The grain size of theperchlorates used in the composition is preferably adjusted by grindingthe product in an air separator.

What is claimed as new and desired to be secured by Letters Patent is:

1. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of silicone resinstable at temperatures of at least 150 C. and having distributedtherethrough as oxidizing salt at least one perchlorate selected fromthe group consisting of alkali metal perchlorates and ammoniumperchlorate, and nitroguanidine as propellant which upon oxidation formsgas for propelling purposes, said oxidizing salt serving as a source ofoxygen for said propellant.

2. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of silicone resinstable at temperatures of at least 150 C. and having distributedtherethrough as oxidizing salt at least one perchlorate selected fromthe group consisting of alkali metal perchlorates and ammoniumperchlorate in an amount equal to between about 50% and of the weight ofsaid propellant composition, and nitroguanidine as propellant which uponoxidation forms gas for propelling purposes in an amount equal tobetween about 10% and 15% of the weight of said perchlorate, saidoxidizing salt serving as a source of oxygen for said propellant.

3. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of silicone resinstable at temperatures of at least C. and having distributedtherethrough ammonium perchlorate as oxidizing salt, and nitroguanidineas propellant which upon oxidation forms gas for propelling purposes,said oxidizing salt serving as a source of oxygen for said propellant.

4. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of hardenedsilicone resin which is stable at temperatures of at least 150 C. andwhich in unhardened condition has a viscosity of between 300 and 2,500centistokes, and having distributed therethrough as oxidizing salt atleast one perchlorate selected from the group consisting of alkali metalperchlorates and ammonium perchlorate, and nitroguanidine as propellantwhich upon oxidation forms gas for propelling purposes, said oxidizingsalt serving as a source of oxygen for said propellant.

5. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of silicone resinstable at temperatures {23 of at least 150 C. and having distributedtherethrough as oxidizing salt at least one perchlorate selected fromthe group consisting of alkali metal perchlorates and ammoniumperchlorate in an amount equal to between about 60% and 70% of theweight of said propellant composition, and nitroguanidine as propellantwhich upon oxidation forms gas for propelling purposes in an amountequal to between about and of the weight of said perchlorate, saidoxidizing salt serving as a source of oxygen for said propellant.

6. A solid propellant composition according to claim 1 wherein saidsilicone resin constitutes between about and of the weight of saidcomposition.

7. A solid propellant composition adapted for use in fire extinguishingdevices, said propellant composition comprising a body of hardenedsilicone resin which is stable at temperatures of at least 150 C. andwhich in unhardened condition has a viscosity of between 300 and 2,500centistokes, said body of silicone resin constituting between about 20%and 30% of the weight of said propellant composition and havingdistributed therethrough ammonium perchlorate in an amount equal tobetween 50% and 70% of the weight of said propellant composition, and aspropellant which upon oxidation forms gas for propellins purposes,nitroguanidine in an amount equal to between about 10% and 15% of theweight of said ammonium perchlorate, said ammonium perchlorate servingas a source of oxygen for said propellant.

0. A method of forming a solid propellant composition adapted for use infire extinguishing devices, said method comprising mix'mg nitroguanidineas a propellant which upon oxidation forms gas for propelling purposes,and a perchlorate selected from the group consisting of alkaline metalperchlorates and ammonium perchlorate as an oxidation salt which servesas source of oxygen for said propellant, with an unhardened siliconeresin adapted to form upon hardening a solid resin body stable attemperatures of at least 150 C.; casting the thusformed mixture in amold of predetermined shape; and hardening said silicone resin, therebyobtaining a silicone resin body having said propellant and saidoxidation salt distributed therethrough.

9. A method of forming a solid propellant composition adapted for use infire extinguishing devices, said method comprising mixing nitroguanidineas a propellant which upon oxidation forms gas for propelling purposes,and ammonium perchlorate as an oxidation salt which serves as a sourceof oxygen for said propellant with an unhardened silicone resin adaptedto form upon hardening a solid resin body stable at temperatures of atleast 150 C.; casting the thus-formed mixture in a mold of predeterminedshape; and hardening said silicone resin, thereby obtaining a siliconeresin body having said propellant and said oxidation salt distributedtherethrough.

10. A method of forming a solid propellant composition adapted for usein fire extinguishing devices, said method comprising mixingnitroguanidine as a propellant which upon oxidation forms gas forpropelling purposes, and a perchlorate selected from the groupconsisting of alkali metal perchlorates and ammonium perchlorate as anoxidation salt which serves as source of oxygen for said propellant withan unhardened silicone resin having a viscosity of between about 300 and2,500 centistokes and adapted to form upon hardening a solid resin bodystable at temperatures of at least 150 C.; casting the thusformedmixture in a mold of predetermined shape; and hardening said siliconeresin, thereby obtaining a silicone resin body having said propellantand said oxidation salt distributed therethrough.

11. A method of forming a solid propellant composition adapted for usein fire extinguishing devices, said method comprising mixing aperchlorate selected from the group consisting of alkali metalperchlorates and ammonium perchlorate in an amount of between about 50%and of the weight of said propellant composition, and nitroguanidine inan amount of between about 10% and 15% of the weight of saidperchlorate, said nitroguanidine serving as a propellant which uponoxidation forms gas for propelling purposes, and said perchlorateserving as an oxidation salt which serves a source of oxygen for saidpropellant, with between about 20% and 30% of the weight of saidpropellant composition of an unhardened silicone resin having aviscosity of between 300 and 2,500 centistokes and being adapted to formupon hardening a solid resin body stable at temperatures of at least C.;casting the thus-formed mixture in a mold of predetermined shape; andhardening said silicone resin, thereby obtaining a silicone resin bodyhaving said propellant and said oxidation salt distributed therethrough.

12. A method of forming a solid propellant composition adapted for usein fire extinguishing devices, said method comprising mixing aperchlorate selected from the group consisting of alkali metalperchlorates and ammonium perchlorate in an amount of between about 50%and 70% of the weight of said propellant composition, aluminum powder inan amount of between 1% and 5% of the weight of said propellantcomposition, and nitroguanidine in an amount of between about 10% and15% of the weight of said perchlorate, said nitroguanidine serving as apropellant which upon oxidation forms gas for propelling purposes, andsaid perchlorate serving as an oxidation salt which serves a source ofoxygen for said propellant, with between about 20% and 30% of the weightof said propellant composition of an unhardened silicone resin having aviscosity of between 300 and 2,500 centistokes and being adapted to formupon hardening a solid resin body stable at temperatures of at least 150C.; casting the thus-formed mixture in a mold of predetermined shape;and hardening said silicone resin, thereby obtaining a silicone resinbody having said propellant and said oxidation salt distributedtherethrough.

References Cited by the Examiner UNITED STATES PATENTS 2,949,352 8/60Cramer 14919 3,014,796 12/61 Long et al. 149-19 3,022,149 2/62 Cramer149-19 3,031,347 4/62 Philipson 14919 X CARL D. QUARFORTH, PrimaryExaminer.

1. A SOLID PROPELLANT COMPOSITION ADAPTED FOR USE IN FIRE EXTINGUISHINGDEVICES, SAID PROPELLANT COMPOSITION COMPRISING A BODY OF SILICONE RESINSTABLE AT TEMPERATURES OF AT LEAST 150*C. AND HAVING DISTRIBUTEDTHERETHROUGH AS OXIDIZING SALT AT LEAST ONE PERCHLORATE SELECTED FROMTHE GROUP CONSISTING OF ALKALI METAL PERCHLOATES AND AMMONIUMPERCHLORATE, AND NITROGUANIDINE AS PROPELLANT WHICH UPON OXIDATION FORMSGAS FOR PROPELLING PURPOSES, SAID OXIDIZING SALT SERVING AS A SOURCE OFOXYGEN FOR SAID PROPELLANT.